The present invention relates to the testing of electronic components, and more particularly, to the test circuitry required for properly verifying the operation of power amplifiers.
It is frequently desirable for electronic components used in applications where reliability is important, to have built-in test functions for verifying that the equipment is operating properly. As a part of these test functions, it is often required that power amplifiers, such as amplifiers used to boost the power of RF signals prior to their delivery to transmitting antennas, include the necessary test circuitry for checking that they are properly operational. While it is sometimes adequate to monitor signal levels during normal operation, some applications require testing independent of or prior to application of normal signal levels. Ordinarily power amplifiers are independently tested by having a special test signal generated by separate test circuitry applied to the input of the amplifier and by then measuring the output of the amplifier, again using separate test circuitry in order to check the response of the amplifier to the test signal. However, this type of test circuit construction requires test signal generating and amplifier output signal measuring capabilities independent of the amplifier itself which are expensive to build into the amplifier system, add significantly to the bulk of the amplifier's electronic package and are subject to many types of operational faults which may provide false indications of amplifier defects. Furthermore, it is difficult to provide separate test circuitry which generates test signals at high power levels and the test functions for power amplifiers are frequently conducted at power levels substantially below the levels characteristic of their actual operation which limits the validity of the test procedure.
It is therefore an obJect of the present invention to provide a test circuit for verifying the independent operation of an amplifier which requires a minimum amount of separate test circuitry and therefore, reduces the bulk of the electronics package associated with the amplifier.
It is another object of the present invention to provide a test circuit for verifying the operation of a power amplifier which tests the operation of the amplifier at power levels characteristic of the operational power levels of the amplifier.
It is a further object of the present invention to provide a test circuit for an amplifier having increased reliability and providing fewer false indications of defects in the actual amplifier itself.